Process for the dehydrochlorination of chlorinated polyolefins

ABSTRACT

THIS INVENTION PERTAINS TO A PROCESS FOR PREPARING DEHYDROCHLORINATED CHLORINATED POLYOLEFINS IN PARTICULATE FORM BY DEHYDROCHLORINATING AN COMMINUTED CHLORINATED POLYOLEFIN CONTAINING CATALYZING AMOUNTS OF A LEWIS ACID, WHILE SAID CHLORINATED POLYOLEFIN IS MAINTAINED IN A FLUIDIZED BED IN THE PRESENCE OF A SUBSTANTIALLY INERT GAS AND FURTHER IN THE PRESENCE OF SMALL AMOUNTS OF AN INERT FILLER WHICH HAS AN AFFINITY FOR ADSORPTION ONTO THE SURFACES OF THE CHLORINATED POLYOLEFIN.

Dec. 19, 1972 R R BLANCHARD ETAL 3,706,724

PROCESS FOR THE DEHYROCHLORINATION OF CHLORINATED POLYOLEFINS 4 Sheets-Sheet 1 Filed July 2, 1971 fem oero/ure probe Z a M m m r r n A m 4 o n k e N 6 O UJ IO N w m d 0 0 n H z r r m M m 2 m e M M 6 4 m MA Mm cm o IC7 F Wu w? 4 N 6 4 2 O Time (Min) Robe/"2 E Rebel-f BY W/A 19 TTORNEY United States Patent Office 3,706,724 Patented Dec. 19, 1972 3,706,724 PROCESS FOR THE DEHYDROCHLORINATION F CHLORINATED POLYOLEFINS Robert R. Blanchard, Port Allen, and James S. Kennedy and Reginald F. Roberts, Baton Rouge, La., assignors to The Dow Chemical Company, Midland, Mich.

Filed July 2, 1971, Ser. No. 159,427 Int. Cl. C081. 27/02, 3/00 US. Cl. 260-943 GD 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Several methods are known which enable chlorinated polyolefins to be vulcanized or crosslinked, e.g. where vulcanization is carried out by subjecting the chlorinated polyolefins before or during the crosslinking process proper for the formation of double bonds to a partial dechlorination, dehydrochlorination or dehydration. Where dehydrochlorination is desired, the chlorinated polyolefins are normally reacted with an acceptor for hydrogen chloride such as the metal oxides, metal hydroxides, metal alcoholates, metal sulfides, metal hydrogen sulfides, metal mercaptides and metal salts of slightly dissociated organic acids, for example, carbonates of alkali metals or alkaline earth metals and the like. Heretofore, such dehydrochlorination has been accomplished by blending the chlorinated polyolefins and the acceptor for hydrogen chloride on heated mill rolls or in high speed mixers such as a Banbury mixer; however, such procedure produces a dehydrochlorinated product in the form of agglomerated particles of relative large mass or as a slabstock, which is diflicultly manageable where subsequent vulcanization or crosslinking is desired.

It is the primary purpose of the present invention to provide a process for producing dehydrochlorination of chlorinated polyolefins at a rapid rate and where the dehydrochlorinated product is in the form of finely divided particles of substantially uniform size.

SUMMARY OF THE INVENTION The above objects are attained by practice of a process comprising (1) preparing a catalyzed chlorinated polyolefin by substantially uniformly admixing from about 0.25 to 0.5 part by weight of a Lewis acid per 100 parts of a comminnted chlorinated polyolefin (phr.), (2) maintaining the catalyzed chlorinated polyolefin in the form of a fluidized bed in the presence of a substantially inert gas and further in the presence of from about 2 to phr. of an inert filler which has an aflinity for adsorption onto the surfaces of the chlorinated polyolefin, .(3) heating the fluidized bed to a temperature sufficient to produce the dehydrochlorination reaction without burning or charring the chlorinated polyethylene being dehydrochlorinated, then (4) cooling the fluidized bed and recovering the dehydrochlorinated product.

DESCRIPTION OF PREFERRED EMBODIMENTS The chlorinated polyolefins which may be readily dehydrochlorinated to form particulate materials may be any comminnted chlorinated polyolefin obtained by chlorination in solution, in the molten state or in aqueous suspension. Of particular desirability, however, are those materials prepared by the suspension chlorination in an inert medium of finely divided essentially linear polyethylene and interpolymers containing at least about 90 mole percent ethylene with the remainder being one or more ethylenically unsaturated comonomers, e.g. the chlorinated polyolefins prepared in aqueous suspension as described in the United States Patent 3,454,544, issued July 8, 1969, and which contain from about 25 to 75 percent by weight chlorine and preferably from about 36 to 48 percent by weight chlorine.

Exemplary of the Lewis acid catalysts which may be used include zinc oxide (in HCl solution), aluminum chloride, magnesium chloride, ferric chloride, cuprous chloride, with zinc chloride being preferred. Such catalysts are used in amounts of from about 0.25 to 0.5 phr. based on chlorinated polyethylene. It has further been discovered, which discovery froms a part of the present invention, that optimum rates of dehydrochlorination were obtained by addition of the Lewis acid to comminnted, wet, chlorinated polyethylene, i.e. wherein said chlorinated polyethylene contained at least about 10 percent by weight water in the polymer particles. These results may be explained on the basis that the catalyst is better able to penetrate the wet chlorinated polyolefin and provide a more thorough and uniform dispersion of the catalyst throughout each polymer particle.

The catalyzed chlorinated polyolefin is then maintained in the form of a fluidized bed by placing such material, in any suitable reactor wherein a substantially inert gas, preferably oxygen, gaseous HCl or nitrogen, may be continuously passed therethrough. At this stage, it is critical to the obtainment of particulate dehydrochlorinated product that the catalyzed chlorinated polyolefin is fluidized in the presence of from about 2 to 5 phr. of an inert filler which has an afiinity for adsorption onto the surface of the chlorinated polyolefin. In this regard, it has been found that magnesium silicate is particularly effective. Exemplary of other useful inert materials are carbon black and titanium dioxide.

It has also been found that unexpectedly enhanced dehydrochlorination rates are attained by the presence in the fluidized bed of from about 0.1 to 1 phr. of an antioxidant material. In this regard, the oxylated diphenylamines have been found to be particularly effective especially when utilized in conjunction with a chlorinated polyolefin containing the prescribed amounts of zinc chloride as the Lewis acid catalyst. This is unexpected as it has been found that such antioxidant by itself, i.e., in the absence of a Lewis acid catalyst, fails to produce any detectable dehydrochlorination of the chlorinated polyolefin. Other antioxidants which have been found to be useful are: dilaurylthiodipropionate, 2,6ditertiary butyl 4-methyl phenol and polymerized l,2dihydro-2,2,4- trimethylquinoline.

For optimum rates of dehydrochlorination, it has been found to be desirable to pre-heat the fluidization reactor, and the fluidizing gases, to a temperature of about 100 C. prior to the addition thereto of the catalyzed chlorinated polyolefin, inert filler and antioxidant. Following addition of the such materials to the fluidizing reactor,

dehydrochlorinated product recovered as a particulate material which is especially adaptable for use in subsequent conventional vulcanization or crosslinking reactions.

The percent dehydrochlorination may be determined by dissolving the dehydrochlorinated product in a solvent such as ortho-dichlorobenzene to which is then added an excess of iodine monochloride in a carbon tetrachloride solution. Iodine is then liberated from unreacted ICl with excess alcoholic potassium iodide. The iodine is then backtitrated with 0.1 N thiosulfate and the percent unsaturation calculated. 7

The following specific examples, wherein all parts and percentages are to be taken by weight, illustrate the present invention but are not to be construed as limiting its scope.

EXAMPLE 1 (A) Preparation of the chlorinated polyolefin In each of a series of experiments, an aqueous slurry comprising from about 3200 to 3600 grams of water and 160 to 180 grams of a polyethylene having an essentially linear and unbranched molecular structure containing less than about 1 methyl group per 100 methylene units in its molecule; a density of about 0.96; an average molecular weight of about 67,000 and which had been prepared using a catalyst composed of triisobutyl aluminum and titanium tetrachloride; was charged to a 1 /2 gallon autoclave with from 6.4 to 7.2 grams of calcium chloride; from to 8 g. of a platy magnesium silicate; about 0.5 cc. of ditertiary butyl peroxide; and from about 24 to 27 drops of a commercially available wetting agent. Each charge was then separately chlorinated, as a first suspension chlorination step, at a temperature of between about 95 and 100 C. until a chlorine content of about 17 percent was obtained.

Following completion of such first chlorination step, each charge was further individually chlorinated in a second suspension chlorination step, at a temperature of 128 C. until a total chlorine content of between about 36 and 48 percent was obtained.

(B) Fluidization apparatus In each of the specific experiments illustrated herein, the designated chlorinated polethylene was formed into a fluid bed utilizing the apparatus set forth in FIG. 1. Such apparatus consists of a 4-foot section of 4-inch I.D. glass pipe wherein air or nitrogen gas was used as the fluidizing medium. Heat was provided by passing the fluidizing gas through electric heaters. Rotameters were installed so that a constant flow of gas could be maintained.

(C) Resin preparation In the preferred process of the present invention, the Lewis acid catalyst was added generally in aqueous solution to particulate chlorinated polyethylene containing at least about 10 percent by weight water. Thereafter the catalyzed chlorinated polyethylene was dried under mild conditions, i.e., at a temperature of about 40f C. under normal pressure. FIG. 2 illustrates the increase in dehydrochlorination rate achieved by utilization of this-procedure as contrasted to blending the Lewis acid catalyst with dried chlorinated polyethylene. Additionally, it has been found that addition of the Lewis acid catalyst during the chlorination. of the polyolefin did not provide dehydrochlorination as the catalyst is substantially completely removed while washing the chlorinated polyolefin subsequent to the chlorination reaction.

FIG. 3 illustrates the comparative eflectiveness of a series of Lewis acids when added to wet chlorinated polyethylene containing 36 percent by weight chlorine at a concentration of 0.5 part by weight. It is apparent that zinc chloride is noticeably the more effective.

FIG. 4 illustrates the effect of zinc chloride concentration on dehydrochlorination rate'when added to wet chlorinated polyethylene and fluidized by the procedure of the present invention.

In the experiments illustrated on FIGS. 2 through 4, 2 to 5 phr. of magnesium silicate and 0.5 phr. of an oxylated diphenylamine (Stalite S) were added to the catalyzed chlorinatedpolyethylene in the fluid bed.

(D) The dehydrochlorination reaction (1) Temperature-As indicated previously, optimum dehydrochlorination rates are obtained by pre-heating the fluidizing gas (and apparatus) to a temperature of about C. prior to the addition of the catalyzed chlorinated polyolefin, inert filler and antioxidant. Thereafter, temperatures up to about 200 C. can be maintained with a temperature of about C. or below being preferred. FIG. 5 illustrates the etfect of various fluidizing temperatures upon dehydrochlorination rate in the absence of an antioxidant. In general, such rate increases in direct relationship with temperature increase.

(2) Antioxidant.FIG. 6 illustrates the effect of fluidization temperature when a zinc chloride catalyzed chlorinated polyethylene, containing 0.5 phr. of an oxylated diphenylamine antioxidant, is dehydrochlorinated by the process of this invention.

A comparison of the data of FIG. 5 and FIG. 6 illustrates the increase in dehydrochlorination rate achieved using the oxylated diphenylamine antioxidant.

FIGS. 7 and 8 illustrates the eflect of antioxidant concentration upon the rate of dehydrochlorination.

(3) Inert filler.--All of the experiments illustrated on FIGS. 2 through 7 included the addition of from 2 to 5 parts per hundred parts of chlorinated polyethylene of magnesium silicate as an inert filler to ensure the attainment of a particulate dehydrochlorinated product. By way of comparison, equivalent experiments but wherein an inert filler of the type as called for by the present invention, was omitted, were characterized by undesirable agglomeration of the dehydrochlorinated product.

What is claimed is:

1. A process for preparing particulate dehydrochlorinated chlorinated polyolefins comprising (1) preparing a catalyzed chlorinated polyolefin by substantially uniformly admixing from about 0.25 to 0.5 part by weight of a Lewis acid per 100 parts of a comminuted chlorinated polyolefin,

(2) maintaining said catalyzed chlorinated polyolefin in the form of a fluidized bed in the presence of a substantially inert gas and further in the presence of from about 2 to 5 parts by weight per 100 parts of chlorinated polyethylene of an inert fil'ler which has an affinity for adsorption onto the surfaces of the chlorinated polyolefin,

(3) heating said fluidized bed to a temperature up to about 160 C. until the desired amount of dehydrochlorination occurs, then (4) cooling said fluidized bed and recovering the dehydrochlorinated product.

2. The process of claim 1 wherein said comminuted chlorinated polyolefin initially contains at least about 10 percent by weight of water.

3. The process of claim 2 wherein said chlorinated polyolefin is chlorinated polyethylene containing from about 36 to 48 percent by weight chlorine.

4. The process of claim 3 wherein said Lewis acid is zinc chloride.

5. The process of claim 4 whereinv said inert filler is magnesium silicate.

6. The process of claim 5 wherein said inert gas is oxygen or nitrogen.

7. The process of claim 2 wherein said fluidized bed additionally contains from about 0.1 to 1 part by weight per 100 parts of chlorinated polyethylene of an antioxidant.

8. The process of claim 7 wherein said antioxidant is an oxylated diphenylamine.

9. A process for preparing particulate dehydrochlorinated chlorinated polyethylene comprising (1) preparing a catalyzed chlorinated polyolefin by substantially uniformly admixing from about 0.25 to 0.5 part by weight of zinc chloride in the form of an aqueous solution per 100 parts of a comminuted chlorinated polyethylene having a chlorine content of between about 36 and 48 percent by weight and containing at least about 10 percent by weight water,

(2) maintaining said catalyzed chlorinated polyethylene in the form of a fluidized bed in the presence of oxygen or nitrogen gas and further in the presence of from about 2 to 5 parts by weight per 100 parts of chlorinated polyethylene of magnesium silicate and from about 0.1 to 1 part by weight per 100 parts of chlorinated polyethylene of an oxylated diphenylamine,

(3) heating said fluidized bed to a temperature up to about 160 C. until the desired amount of dehydrochlorination occurs, then (4) cooling said fluidized bed and recovering the dehydrochlorinated product.

References Qited 5 FOREIGN PATENTS 669,259 8/1963 Canada 26094.9H

OTHER REFERENCES Encyclopedia of Polymer Science and Technology, vol. 10 6, pp. 432-42, John Wiley & Sons, Inc., New York JAMES A. SEIDLECK, Primary Examiner 15 A. HOLLER, Assistant Examiner US. Cl. X.R.

260--88.25, 93.7, 94.9 'H, 677 XA, 696 

